Sweat Kinetics & Amino Acid Loss: The Science of Electrolyte Resorption
The following is a summary of peer-reviewed research by Murphy, Grace R. et al. (2019), published in PLoS One. Read the full article
Ductal Transport Functionality: Eccrine sweat serves as a physiologically "constructed fluid" wherein the active luminal clearance of free amino acids and potassium operates as the driving mechanism to facilitate the ductal resorption of sodium and chloride.
Inverse Resorption Kinetics: Over prolonged exercise, systemic depletion of amino acids (reducing from 6.4 mM to 3.6 mM) and potassium strongly correlates with an exhaustion of ductal reclamation capacity, causing final sweat sodium and chloride concentrations in sweat to elevate significantly by 48.5%. This means that sodium and chloride are lost at faster rates as amino acids and potassium reserves become diminished.
ASCT-1 Co-Transporter Mediation: This localised electrolyte salvage is mediated in part by the ASCT-1 epithelial co-transporter, which exchanges sodium ions symmetrically for small, neutral amino acids—specifically serine and alanine—yielding sweat concentrations up to 26-fold higher than plasma baselines.
Clinical endpoint: The primary clinical endpoint is the maintenance of ductal electrolyte resorption efficiency—evidenced by preventing the progressive elevation of sweat sodium and chloride concentrations and stabilising systemic sodium levels—through the targeted co-replenishment of free amino acids (specifically the high-demand amino acids) and potassium to prevent transporter exhaustion during prolonged exertion